A Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is an auxiliary verifying means which is commonly used in Internet services to fight against automations (i.e. computer programs), and is mainly used in scenarios including account registration, login, forum posting, microblog posting and the like. The quality of a CAPTCHA depends on both a cracking rate by automations and a human passing rate, where the cracking rate by automations means a rate of recognizing CAPTCHA codes by automations, and the human passing rate means a rate of recognizing CAPTCHA codes by ordinary users. The CAPTCHA has a good verification effect if the automatic cracking rate of the CAPTCHA is low and the human passing rate of the CAPTCHA is high. In the existing verification data processing, a total passing rate of a CAPTCHA within one minute is calculated generally according to a formula of total passing rate=[100*C(v)/S(v)]%, where S(v) denotes the number of total verifications of CAPTCHA response information and C(v) denotes the number of correct verifications of CAPTCHA response information (i.e. the number of pieces of CAPTCHA response information passing verifications) within a minute. However, the total passing rate of the CAPTCHA obtained by such method is simple and rough and has low accuracy, and hence is almost useless in estimating the cracking resistance and cracking difficulty of the CAPTCHA.
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